Treatment of wells



Patented May 13, 1952 TREATMENT OF WELLS Joseph B. Clark,

Tulsa, Okla., assignor to Stanclind Oil and Gas Company, Tulsa, porationof Delaware Okla., a cor- No Drawing. Applicati n December 31, 1949,

Serial No. 136,394

23 Claims.

This invention pertains to the treatment of oil and gas wells. Moreparticularly, this invention pertains to a method of increasing theproductivity of an oil or gas well by providing lateral drainagechannels in selected formations adjacent a well. This application is acontinuation-in-part of my application Serial Number 29,932, filed May28, 1948.

In the art of increasing the productivity of oil and gas wells, variousmethods have been proposed for increasing the drainage area within aselected producing zone. For example, nitroglycerin is detonated in awell in some cases either to enlarge the well diameter or fracture theformations immediately adjacent a well. The use of nitroglycerin in thisart is, however, restricted in many cases, due to the presence of pipein the hole, the expense, the hazards, etc. Horizontal drilling islikewise employed to increase the surface area of a well in a selectedzone. The increased productivity, however, is rarely commensurate withthe increased cost. Furthermore, both of these processes are furtherlimited by their inability when used in ordinarydiameter oil or gaswells to extend the drainage channels an appreciable distance into theselected zone. Acidizing is sometimes practiced to increase thepermeability of the formations adjacent a well, but this process isgenerally limited to use in calcareous formations.

Accordingly, it is an object of this invention toprovide an improvedmethod of completing L wells. Another object of this invention is toprovide an improved composition for fracturing producing formations. Amore specific object of this invention is to provide a method offracturing a formation penetrated by a well by injecting a gelled oilyliquid into the formation and subsequently reducing the viscosity ofthis gelled liquid by breaking the gel in situ in the formation, wherebya permeable channel is produced in the formation to conduct fluids fromthe formation into the well. Still another object of this invention isto provide an improved fracturing liquid for deep earth formations, theliquid containing a bodying agent and initially, due tofthe bodyingagent,having a considerably retarded tendency to filter through theformations but eventually having an increased tendency to filter throughthe formations to avoid permanently plugging the flow channels from theformation into the well.

In the present invention, which is directed generally to the art ofproducing permeable channels from oil or gas wells to remote points'peptizer.

in a formation, certain soaps are added to the oily fracturing liquid tobody or gel the oily liquid and produce a highly desirable,low-penetrating liquid. These channels are created by applica tion ofhydrostatic pressure to these low-penetrating oily liquids (ashereinafter defined) sufiicient to produce a crack or fracture in aformation. To produce such a fracture, I first place the low-penetratingliquid in the well opposite the zone to be fractured. Pressure is thenapplied to the liquid; and, due to its retarded tendency to filterthrough the formations, a pressure is built up in the well sufiicient toproduce a fracture, generally along a. bedding plane where the tensilestrength of Stratified rock is weakest. The invention is, however, notlimited to fracturing formations along a horizontal plane foroccasionally, especially in non-Stratified formations, the formationappears to fracture along a vertical plane. In any case, thelow-penetrating liquid is pumped into the well at a rate which causesthe pressure to rise to the point that a fracture occurs. This formationbreakdown pressure is recognized generally by a sharp break orleveling-ofi in pressure after which the liquid may be injected into theformation crevice at high rate without a substantial increase inpressure. This body of gelled low-penetrating liquid in the fracture,having a tendency to retard flow of the interstitial or formation fluidsfrom the formations through the fracture, is removed by the addition ofa gel breaker or by producing the well.

It has been proved. in the laboratory that when a fracture is created ina relatively impermeable core and the fracture is then closed, thepermeability of the core is substantially increased. Laboratory datahave been corroborated in wells where it has also been proved that thepermeability may be further increased by the introduction of formationprops or spacer materials such as sand, crushed shell, small metalobjects, or the like with the low-penetrating liquid or the Preferably,however, I place the props or spacer objects in the low-penetrating,oily liquid which is better adapted, by a higher viscosity and gelstrength, to support the props and carry them into the fracture.

As used in this application, low-penetrating oily liquid is defined asan oily liquid or a liquid miscible with the formation oil which, withrespect to the natural fluids in the well, such as water or crude oil,has a considerably retarded tendency to filter through the formations.Well fluids have a viscosity usually less than about peptizer andcentipoises, frequently 1 to 2 centipoises, with lower values atformation temperatures. A lowpenetrating oily liquid has a viscosity inthe range of from about 30 centipoises to about 5,000 centipoises orhigher, for example, 75 to several hundredcentipoises is preferred.Liquids having higher viscosities can be employed, but

measure of such qualities and is applicableto fluid suspensions ofsolids or fluids containing plastering agents. Filtrate rate iscustomarily defined as the volume of liquid collected in a unit time(normally 30 minutes) when ameasured sample of liquid is placed in acylinder closed at the bottom by a supported filter paper and a gaspressure is placed onthis liquid. The sample is usually 600 cc-.,gaspressure 100 p. s. i., and Whatman No. 50 or'52' filter paper'isused. A fluid loss of 100 cc. or less, preferably 50 cc. or less in 30minutes, is desirable. The filtrate rate of' oil field brines and crudeoils is usually so great. that measurements at 30 minutes aremeaningless. Accordingly, the filtrate rateinsuch cases is determined bythe dehydration time, Where this is defined as the time required for airto blow through the cylinder and filter paper when 600- cc. of theliquid are placed in the cylinder at the start. of the filtrateratetest'and a pressure of 100p. s. i. is applied to the surface ofthefluid. The dehydration time of ordinary crude oils and oil field brinesunder formation conditions is of the order of -30 seconds. Alow-penetrating oily liquid is defined under the-samecondi'tions as afluid having a dehydration time of at least 1.5 minutes, and preferablyat least 3- minutes or more. The filtration apparatus and procedure isdescribed in A. P. I. Code No. 29, second edition, July 1942 (tentative)Usually this dehydration time of loW-pene trating oily liquid will betoolong to measure.

I employ as a viscous oily liquid preferably a higher alcohol, a crudeoil, a refined oil such as gasoline, kerosene, naphtha, fuel oil, dieseloil, aromatic hydrocarbons, an animal oil such as lard oil or fish oil,a vegetable oil such as cottonseed oil, chlorinated hydrocarbons, or thelike containing gelling agents, i. e., an agent which tends to thicken aliquid andthereby reduce substantially its filtrate rate as, forexample, a high molecular weight: linear molecule or polymer, such assalts of the fatty acids, which are at least partially oil solubleordispersable. Soaps, produced by or from aluminum, combined with a fattyacid, produce. suitable bodying agents for the lighter oily liquids.Heating (for example to about 200-260 F. to increase solvation, oradding separately under agitation first the fatty acid and then themetal as the hydroxide, can be employed. The fatty'acid iszpreferablyone of the aliphatic acids carrying at: leastv one carboxyl group inaliphatic chain linkage, the aliphatic chain in either case havingpreferably at least 12 carbon atoms in said chain. Suitable fatty acidcompounds which are available commercially are, for example, cocoanutoil fatty acids, peanut oil fatty acids, palm oil fatty acids, stearicacid, oleic acid, palmitic acid, and the like.

While the salts of fatty acids are, in general, suitable bodying agentsfor producing a suitable viscosity in the hydrocarbon, I prefer toemploy an aluminum soap bodying agent, preferably a hydroxy aluminumsoap, which has the ability to form hydrocarbon gels at ordinarytemperatures. Examples of hydroxy aluminum soap bodying agents are setforth in U. S. 2,390,609, which is entitled Bodying, Agent for LiquidHydrocarbons and which describes specific methods of preparing certainof such hydroxy aluminum soaps. The term hydroxy aluminum soap asemployed herein is intended to mean a soap wherein the hydroxy group orgroups is attached to the aluminum component of the soap rather thanbeing. a component of the fatty acid. A suitable soap of this type, aspointed out in an article entitled Napalm in Industrial and EngineeringChemistry, vol. 38, No. 8 (August 1946), at pages 768-773, can beconsidered as compounded from two distinctive components. One is analuminum laurate or a saturated fatty acid soap containing at least40-50% of this substance or of a functionally related acid soap; thiscomponent is a relatively high-melting solidthat, by itself, producesonlythin and unstable gels. The second component is an aluminum soap orsoaps.

' selected from the group including cycloparafii-nic and unsaturatedacidsthat is, analuminum naphthenate, oleate, oleate-linoleate, etc. Thecombination of an aluminum soap of the laurate type with one or moresoaps of the naphthenateoleate type give a thickening agent ofdistinctivev and superior properties not found in either component andwhen prepared: by the precipitation process, the soap is a solid ofsufliciently high softening point to withstand elevated drying andstorage temperatures. I have found that atabout F., for example, from.about 3% to about 10% of this type soapdisperses in gasoline in fromabout 15 seconds to about 10 minutes and that gels having a suitablefiltrate rate and. viscosity are produced. within from about 30 secondsto about 20 minutes.

I have found that. from: about 0.5% to about 10% by weight relative tothe oily liquid of this hydroxy aluminum: soap, preferably between about3%. and. about'8%;-, produces a suitable gel for fracturing mostformations in: accordance with this. invention. In general, higher.proportions of the soap are required, the higher the average molecularweight ofthehydrocarbon. Where the soap may bedeteriorated as:by-weathering or contaminated as by moisture, it is sometimes desirableto use, even more than. 10%..

It is usually desirable to add the hard, granular material such as sandto increase the likelihood that the fracture will. stay partly open, i.e., be propped open. However, successful treatments have been made whenno such props were added. It may be that this was dueto local spallingfrom the faces of the fracture; the exact reason is not known. The;volume or'weight of sand added is not critical; from no sand uptoconsiderably above 10 pounds to the gallon'of'fracturi-ng liquid can beused. Many wells have been fractured and have shown sustained increases.in oil. well production when usingfrom' 0.15 to 025. pound of sand pergallon; Although the size isnot particularly critical,v graded sandsmaller than about 16-mesh is; desirable. Sand passing through 20- meshsieve and retained on 40-meshsieve is preferred.

In accordance with the preferred: embodiment of this invention, the oilyliquid is. weighed or otherwise measured. and the soap and formationpropsare. addedina tank: as the; liquid is stirred. As stated above,sometimes the liquid may be heated to advantage. If soap which reactsreadily to produce a gel in the oily liquid is employed, a flow-typemixer may be used at the well head for the soap, the props, and the oilyliquid. I have found that the gel will develop in the well. Therefore,since the more viscous gels are diflicult to pump, the soap-liquiddispersion may be introduced into a well before the maximum gelation isreached. Accordingly, when the gelation has proceeded to a point atwhich the viscosityis sufficient to maintain substantially all theparticles of undispersed soap in suspension, the dispersion, includingprops, can be pumped into the well. The gel may be pumped into the welland injected immediately into .the formation or it maybe allowed tostand in the well until the maximum gelation has developed, as indicatedby a sample'retained at the surface. By this means, high viscosityliquids are available for producing the fracture where such liquidswould not be .pumpable by normal pumps.

- In any case, when substantially the maximum gelation of thehydrocarbon has been obtained, it is pumped into position. in a well,preferably into a, confined zoneof awellwhere the fracture is to beproduced, 1. e., a zone in the wellwhich has been isolated by one ormore packers. ,When the low-:penetrating oily liquid reaches theformation, due to its retarded tendency to filter through theformations, a substantial increase in pressure at the surface will benoted. The pressure rises after the viscous liquid or gel reaches theisolated formation until a rather abrupt break or leveling-off in thepressure versus pump rate curve occurs, indicating a formation fracture.If pumping continues at about the same rate, any amount of thelow-penetrating oily liquidmaybeinjected into the formation without asubstantial, increase in pressure. The maximum pressure at the formationis the pressure hereinafter referred to as the formation breakdownpressure and is approximately equivalent, expressed in pounds per squareinch, to. the depth of such formation, in feet. This pressure varies,however, from place to place, depending upon the depth and the nature ofthe formations, folding of the formations, and the like. A weightingmaterial such as barytes, iron filings, iron. oxide, or the like maybeincorporated in the viscous liquid not only as a prop but to produceadditional hydrostatic pressure at the formation. If suflicientweighting material is added, it is sometimes unnecessary to apply pumppres.- sure to "fracture a formation.

A filler fluid, i. e., an inert fluid such as crude oil or a refined-oilsuch as gasoline or kerosene, which has no effect upon the gel, may beinjected into the well after the injection of the viscous liquid toforce the viscous liquid further into the formation. i

Inasmuch as this gelled liquid tends to obstruct the flow of theinterstitial fluids from the fractured formation into the well, it isremoved therefrom after it has produced a fracture of suitableproportions. A peptizer-or gel breaker may be incorporated in the gelledliquid and becomes effective after a time delay. For example,from about1 to about 3% by volume of water, which becomes effective several hoursafter the gelled liquid has reached'the fracture, may be incorporated inthe gelled liquid, as, for example, by emulsification or the like.Likewise, other gel breakers which becomeeifective at the'temperature ofthe formation may be incorporated in 6: the gelled liquid. The gelbreaker may also be injected into the fracture zone prior to or afterthe viscous liquid. In some cases, particularly in deep wells, the heatfrom the formation is sufficient to reduce the viscosity or increase thefilrate rate of the gel so that, without a second liquid, the fracturingliquid may be completely removed from the interstices of the formation.

Among suitable materials for breaking or peptizing the gel and reducingthe viscosity of soaphydrocarbon gels, I have found the water-solubleand oil-soluble amines such as ethanolamine, oleylamine, or similarammoniacal compounds and the oil-soluble sulfonates to be particularlyeffective. Other suitable gel breakers are ammonia, alkali oxides andhydroxides, and the stronger acids. For example, a 5% solution ofhydrochloric, sulfuric, or acetic acid will break practically all 3% to8% soap-hydrocarbon gels. Generally, about 1% to 6% breaker, typically2% to 4%, based upon the volume of the fracturing liquid, diluted with asuitable solvent such as gasoline, is pumped into the well following thefracturing liquid to reduce the viscosity or break the gel so that whenthe well is producedthe sol will flow out of the formation. More breakeris sometimes required, particularly where the soap content is high. Thegel breaker solution may be injected into the formation in any amount,but normally a quantity between about to about 5 times, preferablybetween about and about 2 /2 times, the volume of the low-penetratingoily liquid is injected.

While, as indicated above, the breaker is preferably injected into thefracture through the well following the fracturing liquid, I have foundthat some of the gels, particularly those produced by the hydroxyaluminum soaps, may be broken by the interstitial fluids in mostformations. Breaking the gel by this means is necessarily slow, sincethe gel must be adapted to withstand the peptization effect of the gelbreaker for sufiicient time to permit placement of the gel. Thus, whileit is not generally desirable to break the gel by the action of theinterstitial fluids, due to the necessary delay, such procedure iswithin the purview of this invention.

As pointed out above, props, preferably sand, or similar strong, cheap,granular materials, are incorporated in the viscous liquid either duringmixing or during the time it is being injected into the well. Theseprops, due to the high suspending forces of the viscous liquid, arecarried into the formation fracture with the viscous liquid. Since theseliquids have only a temporary high Viscosity, i. e., since this highviscosity is subsequently broken in the fracture, the props aredeposited in the fracture and held there by the formation as thefracture is collapsed so there is no tendency for the prop-s to flowback into the well as the well is produced and as the sol flows backinto the well.

As an example of the effect of my invention on the operation of aWoodbine sand well, a well in the East Texas Field, which on aproduction test prior to treatment in accordance with my inventionproduced less than 1 barrel of oil per day with no water, was treated asfollows:

The well had 3505 feet of 2-inch tubing with a formation packer locatedon the bottom. Total depth of the well was 3551 feet, and the open holebetween the packer and total depth was 4% inch diameter; A fracturingliquid was made up by adding 6% (by-weight); 9f hydroxy aluminum 7 soap,as above described in the preferred embodiment, to 23 barrels of EastTexas crude oil. The soap was added to the crude oil while the crude oilwas agitated. The crude oil was at a tem perature of about 73 F.Agitation was continued for an hour, at which time the viscosity wasapproximately 200 centipoises on the Stormer viscosimeter operating at600 R. P. M. The filtrate rate of the low-pentrating oily liquid wasabout 20 cc. in 30 minutes. When the viscosity of the fracturing liquidreached 200 centipoises, injection into the well at the rate of 4.68barrels per minute was started with 160 lbs. of 16-mesh screened plastersand being mixed into the fracturing liquid at the pump suction at auniform rate of about 0.15 lb. of sand per gallon of the liquid. Afterthe fracturing liquid had been injected into the tubing, it was followedimmediately by two barrels of East Texas crude oil for the purpose ofseparating or spacing the fracturing liquid from the gel breaker whichthen followed immediately at substantially the sam injection rate. Thisgel breaker, which had been compounded before injection of thefracturing liquid started, consisted of 24 barrels of gasolinecontaining 35 gallons of 60% oil-soluble sulfonates and 40% aromaticpetroleum solvents. Immediately following the gel breaker solution, 25additional barrels of East Texas crude oil were pumped into the well todisplace the gel breaker from the tubing and the well into theformation.

The formation breakdown pressure was approximately 3400 p. s. i., andthe pressure dropped thereafter to the effective overburden pressurewhich was approximately 2700 p. s. i. After the crude oil was injected,the well was allowed to stand idle for 48 hours to permit a substantialreduction in the viscosity of the fracturing liquid. On a productiontest which followed immediately, the well pumped about centipoises crudeoil at the rate of approximately '70 barrels per day. Inasmuch as 122barrels of fluid had been pumped into the well, the initial productionobviously included the injected liquids. However, the sustainedproduction (pumping) was at the rate of 50 barrels of oil per day withno water. Examples of other successful treatments are given in Table I:

In these wells, the volume of gel breaker used was roughly twice thevolume of fracturing fluid. Sand was used at the rate of 0.15 to 0.2pound of 16-mesh sand per gallon of fracturing fluid. Packers were usedto confine the length of zone of open hole to which the hydraulicpressure was applied to the figures given.

While I have described my invention by reference to specificembodiments, it will be apparent that it is susceptible of a greatvariety of embodiments and therefore the invention is not to beconstrued to be limited by the above description. It is defined best bythe appended claims.

Certain subject matter disclosed herein is claimed in Farris applicationSerial No. 136,395,

filed December 31, 1949, as a continuation-inpart of abandoned Farrisapplication Serial No. 29,922, filed May 28, 1948.

I claim:

1. A method of increasing the productivity of a formation penetrated bya well through fracturing the formation, which comprises introducinginto said well a fracturing medium containing as essential constituentsa low-viscosity hydrocarbon liquid and a hydroxy aluminum soapgel-forming material, said soap being in sufficient amount when mixedwith said liquid to produce a fracturing medium possessing a viscosityof at least about I200 centipoises, pumping said fracturing medium intoa confined zone in said well adjacent said formation, pumping additionalliquid into said well after said fracturing medium, until a fracture insaid formation is indicated said additional liquid including a gelbreaker for said fracturing medium, continuing pumping liquid into saidwell to displace at least part of said fracturing medium and at leastpart of said gel breaker into said fracture, whereby the viscosity ofsaid fracturing medium is substantially reduced, and thereafterproducing said well.

2. The method of increasing the fluid productivity of a formationpenetrated by a well, which method comprises introducing into the well apumpable fracturing medium compatible with said fluid, said mediumcomprising a lowviscosity hydrocarbon liquid and between about 3 andabout 8 per cent of a mixture of an aluminum soap of a saturated fattyacid containing at least 40 to 50 per cent of aluminum laurate and analuminum soap of a second acid selected from the group consisting ofcycloparaflinic and unsaturated acids, sufficient to effect gelation ofsaid liquid, whereby said medium is converted into a low-penetratingoily pumpable gel having a viscosity greater than 30 centipoises and adehydration time of at least one and one-half minutes in the apparatusdescribed inv A. P. 1. Code No. 29, second edition, July 1942(tentative) where dehydration time is defined as the time required tofilter 600 cc.i of said gel at p. s. 1. pressure differential, pumpingsaid fracturing medium into the well as a column until a part thereof isin contact with the formation, pumping additional fluid into the well ata rate sufficient to increase the pressure exerted at the formationuntil a formation fracture is indicated by a decrease in the pressure atthe pump discharge while pumping at an undiminished rate, continuing thepumping after indication of the fracture to displace at least a part ofthe fracturing medium from the column into passages formed in theformation, contacting said gel and a gel breaker therefor in an amountand for a time sufficient to reduce substantially the viscosity of theliquid in said passages and thereby prevent clogging of said passages,and withdrawing the liquid of reduced viscosity from the passages byremoving liquids from said well.

3. The method of claim 2 wherein the liquid is crude oil and the amountof soapsis at least 3 per cent by weight based on said liquid.

4. The method of claim 2 wherein the liquid is composed of hydrocarbonsboiling in the gasoline to diesel oil boiling range and the amount ofsoaps is in the range of about 3-8 per cent by weight based onsaid'liquid.

of water is introduced into said fracturing medium prior to itsintroduction into said well.

'7. The method of claim 2 wherein said gel breaker is interstitialliquid in the formation.

8. The method of claim 2 wherein the .gel

.breaker is an amine.

9. The method of. claim 2 wherein the gel breaker is a strong acid.

10. The method of claim 2 wherein the gel breaker isan oil-solublesulfonate.

11. The method of claim 2 in which the soapsand the liquid are mixedbefore introducing said liquid into the well. v

12, The method of claim 11 which includes the steps of mixing the soapswith the liquid until gelation has proceeded to a point at which sandparticles can be suspended in the resulting gel, and suspending sandparticles in' said gel before introducing said gel into the well,whereby said sand particles are carried by said gel into said passagesand deposited therein when'said gel is broken by said gel breaker.

13. The method of claim 2 wherein the fracturing medium comprising soapsand hydrocarbon liquid is introduced into the well before maximumfracturing medium continues in said well.

14. The method of increasing the fluid productivity of a formationpenetrated by a well, which method comprises isolating a portion of thewell adjacent said formation by at least one packer set on the welltubing, preparing a fracturing medium by adding to a low-viscosityhydrocarbon oil about 3-8 per cent by weight of a mixture of soapscomprising aluminum oleate and aluminum coconut oil fatty acid soaps insuch proportions as to effect gelation at atmospheric temperatures of atleast about 75 F., agitating the oil-soap mixture until gelation iseffected to such an extent that the resulting gel will suspend particlesof sand of about 20 to about 40 mesh, adding to the partially gelledmixture from about 0.1 to about 10 pounds of sand per gallon andinjecting the sand-containing gel into the tubing, pumping into thetubing above the fracturing medium a gel-breaker liquid, pumping intothe tubing above the gel-breaker liquid a large quantity of crude oil,continuing the pumping of liquid into the Well until a substantialincrease in pressure at the surface is noted indicating that the gel hasreached the isolated portion of the formation, continuing the pumpinguntil there is a decrease in pump-discharge pressure without substantialdiminution in pumping rate, thus indicating a formation fracture,further continuing the pumping of liquid into the formation to enlargechannels formed therein, thereby carrying sand into said channels andeven tually carrying gel breaker into said channels, then discontinuingthe pumping and allowing the well to stand idle for a period of hours topermit reversion of the gel to a low-viscosity liquid by gel breakerassociated therewith in said channels and deposition of the sand in saidchannels, and finally producing well fluids from said isolated sectionto effect removal of the reverted gel from the channels.

15. The method of increasing the fluid productivity of a formationpenetrated by a well, which method comprises isolating a portion of thewell .30 gelation is effected, whereby gelation of said '10 adjacentsaid formation by at least one packer seton the well tubing, preparing afracturing medium by adding a low-viscosity hydrocarbon oil about 3 to 8per cent by weight of a mixture of an aluminum soap of coconutoil fattyacids and an aluminum soap of fatty acids selected from the groupconsisting of cycloparafiinic and unsaturated fatty acids, and therebyforming a dispersion capable ofefiecting gelation at atmospherictemperatures of'at least about F., agitating the oil-soap mixture untilgelation is effected to such an extent that the resulting gel willsuspend particles of sand of about 20 to about 40 mesh, adding to thepartially gelled mixture from about 0.1 to about 10 pounds of sand pergallon and injecting the sand-containing gel into the tubing, pumpinginto the tubing above the fracturing medium a gel-breaker liquid,pumping into the tubing above the gelbreaker liquid a large quantity ofoil, continuing the pumping of liquid into the well until a substantialincrease in pressure at the surface is noted indicating that the gel hasreached the isolated portion of the formation, continuing the pumpinguntil there is a decrease in the resistance to flow of said gel whichindicates a formation fracture, further continuing the pumping of liquidinto the formation to enlarge channels formed therein, thereby carryingsand into said channels and eventually carrying gel breaker into saidchannels, then discontinuing the pumping and allowing the well to standidle for a period of hours to permit reversion of the gel to alow-viscosity liquid by gel breaker associated therewith in saidchannels and deposition of the sand in said channels, and finallyproducing well fluids from said isolated section to effect removal ofthe reverted gel from the channels.

16. The method of increasing the fluid productivity of a formationpenetrated by a well comprising the steps of introducing into the well afracturing medium comprising a low-viscosity hydrocarbon oil and fromabout 3 to about 8 per cent by weight of a mixture of an aluminum soapof saturated fatty acids and an aluminum soap of a fatty acid selectedfrom the group consisting of cycloparafiinic and unsaturated fattyacids, thereby forming a dispersion capable of effecting gelation attemperatures of at least about 75 F., agitating the oil-soap mixtureuntil it is partially gelled to such an extent that will suspendparticles of sand of about 20 to about 40 mesh, adding to the partiallygelled mixture from about 0.1 to about 10 pounds per gallon of sand ofabout 20 to 40 mesh, disposing a quantity of said partially gelledmixture with said sand suspended therein within a confined zone in saidwell adjacent said formation, retaining said quantity in said confinedzone, whereby increased gelation developes, applying to said quantity apressure sufilcient to fracture said formation and inject at least apart of said gel and said sand into passages formed in said formation,contacting'said gel and a breaker therefor to cause a reduction in theviscosity of said gel in said passages and resolution of said gel into arelatively low-viscosity liquid whereby said relatively low-viscosityliquid will be removed from said well when liquids are produced fromsaid well.

17. A method of increasing the productivity of a formation penetrated bya well comprising the steps of mixing at the well head a hydrocarbonliquid and an aluminum soap gelling agent for said liquid in sufficientproportion to form a lowpenetrating gel which is cap-able of breaking on"assess-4 prolonged contact with intersticial liquid, .pumping thismixture into said well, forcing said mixture down said well duringge'latiojn of said mixture, whereby a more viscous gel may "bepositioned in a confined zone adjacent said formation than could bereadily pumped, increasing the pressure on said gel until a formationfracture is indicated, continuing application of high pressure to forcea portion of said gel into said fracture, and producing .fiuids fromsaid well only after maintaining said gel in said fracture for a timesuficient to break and reduce substantially the viscosity of said .gel.

1-8. The method of claim 17 which includes the step of adding granularspacer material insoluble in well fluids with at least .a portion of theliquid introduced into the well whereby 'said spaced material maybecarried by the gel into the formation fracture and deposited in saidfracture when the gel is broken.

19. A .method according to claim 17 wherein said aluminum soap gellingagent is a .hydroxy aluminum soapgelling agent.

20. The methodof claim .17 wherein the hydrocarbon liquid is crude oil.and the amount of 22. The method of claim 17 which includes the step'of introducing a gel breaker through said well into said fracture toexpedite the breaking of said gel.

23. A method of claim 22 wherein said gel breaker comprises betweenabout 1 and about 3 percent by volume of water based upon the volume ofsaid gel.

JOSEPH B. CLARK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,264,353 Zimm'er et al Dec. 2,1941 2,300,325 Leeuwen Oct. 27, 1942 -.2,33'2;822 Williams Oct. 26, 19432,354,570 "Benckenstein July 25, 1944 2,379,516 Garrison July 3, 19452,380,893 'ZiIIIIneret a1 Juli 31, 1945 2,390,609 Minich Dec, 11, 19452,447,064 Ge'bh'art-etal Aug. 17, 1948 2,458,034 Swenson et a1 Jan. 4,1949 "2,477,296 Georgi July 26, 1949 2,491,641 Bondi Dec. 20, 1949 OTHERREFERENCES Torrey, P. D.: Selective Exclusion of Fluids from Wells,'TheOil Weekly, pages 26 to 35, May 22, 1939.

Napalm, Fieser et 2.1. Industrial and Eng. Chem., vol. 36, No. 8, Aug.1946, pp. 768-773.

1. A METHOD OF INCREASING THE PRODUCTIVITY OF A FORMATION PENETRATED BYA WELL THROUGH FRACTURING THE FORMATION, WHICH COMPRISES INTRODUCINGINTO SAID WELL A FRACTURING MEDIUM CONTAINING AS ESSENTIAL CONSTITUENTSA LOW-VISCOSITY HYDROCARBON LIQUID AND A HYDROXY ALUMINUM SOAPGEL-FORMING MATERIAL, SAID SOAP BEING IN SUFFICIENT AMOUNT WHEN MIXEDWITH SAID LIQUID TO PRODUCE A FRACTURING MEDIUM POSSESSING A VISCOSITYOF AT LEAST ABOUT 200 CENTIPOISES, PUMPING SAID FRACTURIN MEDIUM INTO ACONFINED ZONE IN SAID WELL ADJACENT AND FORMATION, PUMPIN ADDITIONALLIQID INTO SAID WELL AFTER SAID FRACTURING MEDIUM, UNTIL A FRACTRE INSAID FORMATION IS INDICATED SAID ADDITIONAL LIQUID INCLUDING A GELBREAKER FOR SAID FRACTURING MEDIUM, CONTINUING PUMPING LIQUID INTO SAIDWELL TO DISPLACE AT LEAST PART OF SAID FRACTURING MEDIUM AND AT LEASTPART OF SAID GEL BREAKER INTO SAID FRACTURE, WHEREBY THE VISCOSITY OFSAID FRACTURING MEDIUM IS SUBSTANTIALLY REDUCED, AND THEREAFTERPRODUCING SAID WELL.